1. Field of the Invention
The present invention relates to ice condensers for pressurized water nuclear reactors and to methods of maintaining the ice in such ice condensers. More specifically, the invention relates to a vibrating assembly for vibrating the ice baskets of an ice condenser of a pressurized water reactor, and to a method of maintaining the ice in the ice baskets using such a vibrating assembly.
2. Related Art
There are two types of nuclear reactors generally used in the United States, the boiling water reactor and the pressurized water reactor. In commercial nuclear plants, the reactor is housed in a building called a containment structure. In a catastrophic accident in which one of the pipes attached to the reactor breaks, the contents of the pipe are released into the containment structure.
In boiling water reactors, steam released in the event of a catastrophic accident fills the containment structure and then is forced into a pool of water, so as to suppress the steam and reduce the pressure in the containment structure.
In pressurized water reactors, the reactor is housed in a large "dry" containment structure. The size and strength of the containment holds the steam in the event of an accident. However, in one version of a pressurized water reactor, a suppression system is included to condense steam released during an accident. This suppression system is known as an ice condenser, and was developed by Westinghouse Electric Corporation. An early example of such a suppression system is the subject of U.S. Pat. No. 3,580,806 to Weems et al and assigned to Westinghouse.
In the ice condenser suppression system, fragmented ice is maintained in baskets located in the containment structure. In the event of an accident, the steam released from a broken pipe is channeled into the ice baskets to reduce the pressure in the containment and prevent the release of radioactive steam outside the containment.
Due to melting and sublimation, voids tend to form in the body of fragmented ice, and pieces of fragmented ice may become fused together. In order to minimize these problems, Weems et al propose a system for reducing the thermal gradients, and in turn the convection currents to which the ice fragments are exposed. However, even with such a system, melting and sublimation cannot be eliminated. Consequently, the prior art has developed a number of systems for maintaining the bodies of fragmented ice. U.S. Pat. Nos. 3,850,002; 4,659,068; 4,671,920; 4,711,755; and 4,723,611 are illustrative of such systems. These systems tend to be mechanically complicated, and to be directed to recharging or replenishing the supply of ice, rather that maintaining the ice in optimum condition so as to delay the need for recharging.
It is to the solution of these and other problems to which the present invention is directed.